Unit 2.3a

Question 1

What is sexual reproduction?

Answer 1

Is the production of new living organisms by combining genetic information from two individuals of different sexes

Question 2

What is asexual reproduction?

Answer 2

It’s a mode of reproduction, by which offspring arise from a single organism, and inherit the genes from that parent only

Question 3

What are the two disadvantages of sexual reproduction?

Answer 3

1. Only half a population are able to produce offspring
2. It disrupts a successful genome from a parent as it only passes half onto each offspring

Question 4

In sexually reproducing species, what is the ratio of male to female offspring?

Answer 4

Half male, half female

Question 5

Is asexual or sexual reproduction more time efficient?

Answer 5

Asexual reproduction is more efficient as all offspring are able to reproduce which increases the reproduction rate in comparison to sexual reproduction, where only female offspring can reproduce

Question 6

What is the paradox of the existence of males?

Answer 6

Males are not able to reproduce so sexually reproducing species are at a disadvantage as the number of offspring they produce is outcompeted by asexual species.

Question 7

What does sexual reproduction disrupt?

Answer 7

The successful genomes of each parent, as the number of chromosomes must be halved to go in each gamete

Question 8

How do you sexually reproducing eukaryotes halve the number of chromosomes present in each gamete?

Answer 8

Process of meiosis

Question 9

In sexual reproduction, when are the halves of chromosomes recombined?

Answer 9

During fertilisation

Question 10

Can you predict the alleles that will be present in each gamete?

Answer 10

No, this is a random process as a result of crossing over and independent assortment

Question 11

Is the mating process in sexual reproduction, beneficial or not beneficial and if so why or why not? (3 points)

Answer 11

The mating process in sexual reproduction is not beneficial and here are three reasons why:
- Energy expenditure involved in courtship
- Energy expenditure, involved in mating
- Increase predation risk during mating, courtship, or due to sexually selected traits

Question 12

What are three advantages to sexual reproduction?

Answer 12

1. Greater genetic variation in species, maintaining a large gene pool.
2. Variation means organisms can cope with selection pressures evolve to changing environmental situations.
3. Provide raw material required to keep running in the red Queens arm race between parasites and hosts.

Question 12

Why is sexual reproduction important?

Answer 12

Allows organisms to adapt to changing environments and threats, posed by predators and parasites

Question 13

What is variation?

Answer 13

It’s the differences between individuals in a population, determined by the alleles that are inherited

Question 14

When would a host be described to have greater fitness?

Answer 14

When it can resist and tolerate parasites

Question 15

When would a parasite be described as having greater fitness?

Answer 15

When is able to feed and reproduce and find new hosts

Question 16

Is sexual reproduction or asexual reproduction, more beneficial for hosts?

Answer 16

Sexual reproduction as the genetic variability of the offspring, reduces the chances that they will be susceptible to infection by parasite

Question 17

When is maintaining the genome of a parent an advantage? (Asexual reproduction.)

Answer 17

It’s an advantage in very narrow, stable niches or when recolonising distributed habitats

Question 18

What are three disadvantages to asexual reproduction?

Answer 18

1. Offspring are genetic clones so lack variation and struggle to adapt to changes in environment. However, mutations can occur which provide some variation and so some natural selection and evolution can occur.
2. It can produce lots of offspring in a small space so there is high competition for food and space.
3. Unfavourable conditions such as extreme temperature can wipe out entire colonies.

Question 19

What are the two types of reproduction in eukaryotes?

Answer 19

Vegetative cloning
- occurs in plants, using runners, bulbs, or tubers

Parthenogenesis
- Reproduction from female gamete with no fertilisation. Common in cool climates, which are disadvantages to parasites or were there is low parasite density/diversity.

Question 20

What species usually use pathogenesis?

Answer 20

Bees, wasps and ants

Question 20

Does pathogenesis occur in vertebrates?

Answer 20

It only occurs in one in a thousand species and is common in fish, amphibians and reptiles, but not mammals

Question 21

Can species produce both asexually and sexually?

Answer 21

Yes, daphnia are an example. When conditions are favourable and rapid growth is needed the reproduce asexually by pathogenesis. When conditions are not favourable and there is a lack of food and poor temperature, they reproduce sexually.
Sexual reproduction allows genetic variation increasing survival.

Question 22

What are three less discussed forms of asexual reproduction?

Answer 22

1. Budding - yeast does this, it’s when offspring grow out of a parents body
2. Binary fission - similar to mitosis, this is how bacteria reproduce.
3. Fragmentation - fragment of plant or animal breaks off and grows into new individual, some starfish do this

Question 23

Why can horizontal gene transfer be beneficial to asexual reproduction?

Answer 23

Increases variation in organisms

Question 24

Which is faster, vertical or horizontal gene transfer?

Answer 24

Horizontal

Question 25

Why is horizontal gene transfer beneficial for bacteria and yeast?

Answer 25

Plasmids can be transferred between the individuals